[dpdk-dev] [PATCH 0/2] prevent out of bounds read with checksum

Bruce Richardson bruce.richardson at intel.com
Mon Dec 17 16:50:03 CET 2018


The functions for checksumming the packet payload don't perform bounds
checks, and are used by the TAP driver which does not do any bounds checks
on the incoming packet either. This means a packet received with an
incorrect IP header can read beyond the end of the mbuf.

In the worst case, where the length is specified as being smaller than the
IPv4 header, 32-bit wrap-around on subtraction occurs, meaning that approx
4GB of memory will be read.

To fix this, we can introduce a sanity check into the ipv4 function to
ensure that underflow does not occur. Since the checksum function does not
take the mbuf length as a parameter, we cannot check for overflow there,
so we instead perform the checks in the TAP driver directly.

Ideally, in a future release, all checksum functions should be modified to
take a max buffer length parameter to fix this issue globally.

NOTE: It appears that the dpaa driver also uses these functions, but from
what I can see there, they are only used on TX, which means that there
should be less need for parameter length checking, as the data does not
come from an untrusted source. Perhaps maintainers, Hemant and Shreyansh,
can confirm?

CC: Hemant Agrawal <hemant.agrawal at nxp.com>
CC: Shreyansh Jain <shreyansh.jain at nxp.com>

Bruce Richardson (2):
  net: fix underflow for checksum of invalid IPv4 packets
  net/tap: add buffer overflow checks before checksum

 drivers/net/tap/rte_eth_tap.c | 14 ++++++++++++++
 lib/librte_net/rte_ip.h       | 12 ++++++++----
 2 files changed, 22 insertions(+), 4 deletions(-)

-- 
2.19.2



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